Open loop MIMO mode for LTE-A uplink

ABSTRACT

A precoding scheme to accommodate user equipment (UEs) having higher Doppler speeds. In such transmission schemes, a different precoding matrix is applied to each orthogonal frequency division multiplex (OFDM) symbol in the transmission stream. Additionally, a downlink control message format is defined to handle assignment of multiple different transmission schemes using the same message format. The downlink control message format includes a control element in one of the message fields along with a set of parameters specifically applicable to the assigned transmission scheme. Based on the value of this control element, the UE sets the specific transmission scheme and determines a set of interpretation rules uniquely associated with that transmission scheme. Using the interpretation rules, the UE is able to read the set of parameters as applied to the selected transmission scheme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/376,639, entitled, “OPEN LOOP MIMO MODE FOR LTE-AUPLINK”, filed on Aug. 24, 2010, which is expressly incorporated byreference herein in its entirety.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to techniques for allocating and using transmissionresources in a multi-input multi-output (MIMO) wireless communicationsystem.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication content such as voice, video, packet data, messaging,broadcast, etc. These wireless systems may be multiple-access systemscapable of supporting multiple users by sharing the available systemresources. Examples of such multiple-access systems include CodeDivision Multiple Access (CDMA) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA)systems.

A wireless communication system may include a number of base stationsthat can support communication for a number of user equipments (UEs). Abase station may include multiple transmit and/or receive antennas. EachUE may include multiple transmit and/or receive antennas. UEs maytransport in the uplink using transport block assignments indicated bythe base station. In conventional wireless systems, such as thecurrently agreed upon version of the Long Term Evolution (LTE), thetransmission in the uplink direction may be performed either as a singleinput, multiple output (SIMO) or as a closed loop MIMO transmission.With the introduction of UEs with up to four antennas in the LTEAdvanced (LTE-A) specification, additional uplink transmission schemesmay improve performance.

SUMMARY

Representative aspects of the present disclosure are directed to aprecoding scheme to accommodate UEs having a higher Doppler speed, whichcauses the channel seen by the UEs to change rapidly, even within onesubframe of time, 1 ms, including a sequence of OFDM symbols. In suchtransmission schemes, a different precoding matrix is applied to eachOFDM symbol in the transmission stream. In some example aspects, theprecoding matrices may be selected from a known library of precodingmatrices (e.g., a standard library), while in other example aspects, theUE may permute each precoding matrix selected from the known library toincrease application of the same set of matrix layers.

In another representative aspect of the present disclosure, a downlinkcontrol message format is defined to handle assignment of multipledifferent transmission schemes using the same message format. Suchdownlink control messages include a control element in one of themessage fields along with a set of parameters. Based on the value ofthis control element, the UE sets a specific transmission scheme anddetermes a set of interpretation rules uniquely associated with thattransmission scheme. Using the interpretation rules, the UE is able toread the set of parameters as applied to the selected transmissionscheme.

In one aspect of the disclosure, a method of precoding multiple OFDMsymbols in an uplink transmission stream, including assigning a firstprecoding matrix to a first OFDM symbol and assigning a second precodingmatrix to a second OFDM symbol, where the second precoding matrix isdifferent from the first precoding matrix.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for assigning a first precodingmatrix to a first OFDM symbol; and means for assigning a secondprecoding matrix to a second OFDM symbol, where the second precodingmatrix is different from the first precoding matrix.

In an additional aspect of the disclosure, a computer program producthas a computer-readable medium having program code recorded thereon.This program code includes code to assign a first precoding matrix to afirst OFDM symbol and code to assign a second precoding matrix to asecond OFDM symbol, where the second precoding matrix is different fromthe first precoding matrix.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes at least one processor and a memorycoupled to the processor and is configured to assign a first precodingmatrix to a first OFDM symbol and assign a second precoding matrix to asecond OFDM symbol, where the second precoding matrix is different fromthe first precoding matrix.

In another aspect of the disclosure, a method for wireless communicationincludes identifying a selected transmission scheme from multipletransmission schemes suitable for UE communication, selecting a controlelement associated with the selected transmission scheme, generating aDCI message using the control element and a set of parameters uniquelyassociated with the selected transmission scheme, and transmitting theDCI message to the UE.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for identifying a selectedtransmission scheme from multiple transmission schemes suitable for UEcommunication, means for selecting a control element associated with theselected transmission scheme, means for generating a DCI message usingthe control element and a set of parameters uniquely associated with theselected transmission scheme, and means for transmitting the DCI messageto the UE.

In an additional aspect of the disclosure, a computer program producthas a computer-readable medium having program code recorded thereon.This program code includes code to identify a selected transmissionscheme from multiple transmission schemes suitable for UE communication,code to select a control element associated with the selectedtransmission scheme, code to generate a DCI message using the controlelement and a set of parameters uniquely associated with the selectedtransmission scheme, and code to transmit the DCI message to the UE.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes at least one processor and a memorycoupled to the processor and is configured to identify a selectedtransmission scheme from multiple transmission schemes suitable for UEcommunication, to select a control element associated with the selectedtransmission scheme, to generate a DCI message using the control elementand a set of parameters uniquely associated with the selectedtransmission scheme, and to transmit the DCI message to the UE.

In another aspect of the disclosure, a method for wireless communicationincludes receiving a downlink control message from a base station,reading a control element from the downlink control message, setting anuplink transmission scheme based on the control element, determining aset of interpretation rules uniquely associated with the controlelement, and interpreting a set of parameters within the downlinkcontrol message according to the set of interpretation rules.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes means for receiving a downlink controlmessage from a base station, means for reading a control element fromthe downlink control message, means for setting an uplink transmissionscheme based on the control element, means for determining a set ofinterpretation rules uniquely associated with the control element, andmeans for interpreting a set of parameters within the downlink controlmessage according to the set of interpretation rules.

In an additional aspect of the disclosure, a computer program producthas a computer-readable medium having program code recorded thereon.This program code includes code to receive a downlink control messagefrom a base station, code to read a control element from the downlinkcontrol message, code to set an uplink transmission scheme based on thecontrol element, code to determine a set of interpretation rulesuniquely associated with the control element, and code to interpret aset of parameters within the downlink control message according to theset of interpretation rules.

In an additional aspect of the disclosure, an apparatus configured forwireless communication includes at least one processor and a memorycoupled to the processor and is configured to receive a downlink controlmessage from a base station, to read a control element from the downlinkcontrol message, to set an uplink transmission scheme based on thecontrol element, to determine a set of interpretation rules uniquelyassociated with the control element, and to interpret a set ofparameters within the downlink control message according to the set ofinterpretation rules.

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram conceptually illustrating an example of amobile communication system.

FIG. 2 is a block diagram conceptually illustrating a design of a basestation/eNB and a UE configured according to one aspect of the presentdisclosure.

FIG. 3A is a block diagram illustrating an example of a conceptualtransmission sequence of OFDM symbols.

FIG. 3B is a block diagram illustrating a conceptual transmissionsequence of OFDM symbols configured according to one aspect of thepresent disclosure.

FIG. 3C is a functional block diagram illustrating example blocksexecuted to implement one aspect of the present disclosure.

FIG. 3D. is a block diagram illustrating a conceptual wirelesscommunication apparatus configured according to one aspect of thepresent disclosure.

FIG. 4 is a block diagram illustrating a conceptual sequence of precodermatrices used in a MIMO system according to one aspect of the presentdisclosure.

FIG. 5 is a block diagram illustrating another conceptual sequence ofprecoder matrices used in a MIMO system according to one aspect of thepresent disclosure.

FIG. 6 is a functional block diagram illustrating example blocksexecuted to implement one aspect of the present disclosure.

FIG. 7 is a block diagram representation of a wireless communicationtransmitter apparatus configured according to one aspect of the presentdisclosure.

FIG. 8 functional block diagram illustrating example blocks executed toimplement one aspect of the present disclosure.

FIG. 9 is a block diagram representation of a wireless communicationreceiver apparatus configured according to one aspect of the presentdisclosure.

DETAILED DESCRIPTION

As previously discussed, the introduction of additional antennaconfigurations of a UE may require signaling on the downlink to supportadditional SIMO or MIMO modes of transmission. In conventional LTEsystems, downlink control information (DCI) messages signal one of twomodes: SIMO or MIMO closed loop. To achieve improved performance, forexample, when UEs are experiencing high Doppler fading (e.g., a fastmoving UE), new MIMO modes are desirable.

As discussed in details below, a new syntactical element for signalingDCI message is introduced. The fields of the new DCI message areprovided to enable signaling of either a closed loop rank 1 MIMO mode oran open loop MIMO mode using different values of a field of the DCImessage. Furthermore, in one aspect, a field is provided in the new DCImessage. The interpretation of this field is context-sensitive dependingupon a rank value indicated in another field of the new DCI message. Thesignaling of rank 1 scheme, as discussed in details below, may be usefulin situations when a UE is at the edge of a cell, or when a channelbetween a UE and a base station is highly correlated. Open loop MIMOsignaling, as discussed in details below, may be useful for fast movingUEs or for UEs in high geometry cases.

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radiotechnology such as Global System for Mobile Communications (GSM). AnOFDMA system may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA, which employs OFDMA on the downlink and SC-FDMA on theuplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the systems and radiotechnologies mentioned above as well as other systems and radiotechnologies. For clarity, certain aspects of the techniques aredescribed below for LTE, and LTE terminology is used in much of thedescription below.

FIG. 1 shows a wireless communication system 100, which may be an LTEsystem or some other system. System 100 may include a number of evolvedNode Bs (eNBs) 110 and other network entities. An eNB may be an entitythat communicates with the UEs and may also be referred to as a basestation, a Node B, an access point, etc. Each eNB 110 may providecommunication coverage for a particular geographic area and may supportcommunication for the UEs located within the coverage area. To improvecapacity, the overall coverage area of an eNB may be partitioned intomultiple (e.g., three) smaller areas. Each smaller area may be served bya respective eNB subsystem. In 3GPP, the term “cell” can refer to thesmallest coverage area of an eNB 110 and/or an eNB subsystem servingthis coverage area.

UEs 120 may be dispersed throughout the system 100, and each UE 120 maybe stationary or mobile. A UE may also be referred to as a mobilestation, a terminal, an access terminal, a subscriber unit, a station,etc. A UE 120 may be a cellular phone, a personal digital assistant(PDA), a wireless modem, a wireless communication device, a handhelddevice, a laptop computer, a cordless phone, a wireless local loop (WLL)station, a smart phone, a netbook, a smartbook, a tablet, etc.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition a frequency range into multiple(K_(s)) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K_(s))may be dependent on the system bandwidth. For example, K_(s) may beequal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5,5, 10 or 20 mega-Hertz (MHz), respectively. The system bandwidth maycorrespond to a subset of the K_(s) total subcarriers.

FIG. 2 shows a block diagram of a design of an exemplary basestation/eNB 110 and a UE 120, which may be one of the eNBs and one ofthe UEs in FIG. 1. A UE 120 may be equipped with T antennas 1234 athrough 1234 t, and base station 110 may be equipped with R antennas1252 a through 1252 r, where in general T≧1 and R≧1.

At UE 120, a transmit processor 1220 may receive data from a data source1212 and control information from a controller/processor 1240. Transmitprocessor 1220 may process (e.g., encode, interleave, and symbol map)the data and control information and may provide data symbols andcontrol symbols, respectively. Transmit processor 1220 may also generateone or more demodulation reference signals for multiple non-contiguousclusters based on one or more RS sequences assigned to UE 120 and mayprovide reference symbols. A transmit (TX) multiple-inputmultiple-output (MIMO) processor 1230 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, and/or thereference symbols from transmit processor 1220, if applicable, and mayprovide T output symbol streams to T modulators (MODs) 1232 a through1232 t. Each modulator 1232 may process a respective output symbolstream (e.g., for SC-FDMA, OFDM, etc.) to obtain an output samplestream. Each modulator 1232 may further process (e.g., convert toanalog, amplify, filter, and upconvert) the output sample stream toobtain an uplink signal. T uplink signals from modulators 1232 a through1232 t may be transmitted via T antennas 1234 a through 1234 t,respectively.

At base station 110, antennas 1252 a through 1252 r may receive theuplink signals from UE 120 and provide received signals to demodulators(DEMODs) 1254 a through 1254 r, respectively. Each demodulator 1254 maycondition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain received samples. Each demodulator1254 may further process the received samples to obtain receivedsymbols. A channel processor/MIMO detector 1256 may obtain receivedsymbols from all R demodulators 1254 a through 1254 r. Channel processor1256 may derive a channel estimate for a wireless channel from UE 120 tobase station 110 based on the demodulation reference signals receivedfrom UE 120. MIMO detector 1256 may perform MIMO detection/demodulationon the received symbols based on the channel estimate and may providedetected symbols. A receive processor 1258 may process (e.g., symboldemap, deinterleave, and decode) the detected symbols, provide decodeddata to a data sink 1260, and provide decoded control information to acontroller/processor 1280.

On the downlink, at base station 110, data from a data source 1262 andcontrol information from controller/processor 1280 may be processed by atransmit processor 1264, precoded by a TX MIMO processor 1266 ifapplicable, conditioned by modulators 1254 a through 1254 r, andtransmitted to UE 120. At UE 120, the downlink signals from base station110 may be received by antennas 1234, conditioned by demodulators 1232,processed by a channel estimator/MIMO detector 1236, and furtherprocessed by a receive processor 1238 to obtain the data and controlinformation sent to UE 120. Processor 1238 may provide the decoded datato a data sink 1239 and the decoded control information tocontroller/processor 1240.

Controllers/processors 1240 and 1280 may direct the operation at UE 120and base station 110, respectively. Processor 1220, processor 1240,and/or other processors and modules at UE 120 may perform or directprocess 800 in FIG. 8 and/or other processes for the techniquesdescribed herein. Processor 1256, processor 1280, and/or otherprocessors and modules at base station 110 may perform or direct process600 in FIG. 6 and/or other processes for the techniques describedherein. Memories 1242 and 1282 may store data and program codes for UE120 and base station 110, respectively. A scheduler 1284 may scheduleUEs for downlink and/or uplink transmission and may provide allocationsof resources (e.g., assignment of multiple non-contiguous clusters, RSsequences for demodulation reference signals, etc.) for the scheduledUEs.

Certain uplink transmissions schemes are available to the UE 120 fortransmission to an eNodeB 110. The precoding matrix (or vector) may beswitched per OFDM symbol. The precoding matrices used in each OFDMsymbol are derived from the agreed codebook in the 3GPP TS 36.211document.

FIG. 3A is a block diagram illustrating a portion 300 of an uplinksignal transmitted by the UE 120. In LTE-A, the upstream transmissionuses single carrier frequency domain multiplexing (SC-FDM). The signalportion 300 depicts 12 OFDM data symbol transmissions with two referencesignal (RS) transmissions interspersed within the 14 symbols of the twoillustrated slots. Currently, the same precoding matrix (or vector) isused for each OFDM symbol (e.g., 300-0-300-2, 300-4-300-9,300-11-300-13) of the transmission stream. The precoding matrices usedfor the OFDM symbols are currently derived from a codebook in the 3GPPTS 36.211 document. Using the same precoding matrix may be morebeneficial when reliable channel knowledge is available. With a highDoppler (e.g., the UE is moving quickly) the channels change morequickly, therefore, the channel knowledge becomes less reliable.

Instead of keeping the same precoding matrix with each OFDM symbol,various aspects of the present disclosure provide for switching theprecoding matrix (or vector) for each OFDM symbol. With reference toFIG. 3B, another portion 301 of a signal transmitted by the UE 120 isshown. Each OFDM symbol (e.g., 301-0-301-2, 301-4-301-9, 301-11-301-13)uses a different precoding matrix (precoders 0-11). The precoder used ineach OFDM symbol (e.g., 301-0-301-2, 301-4-301-9, 301-11-301-13) in FIG.3B may each be selected from the precoding matrices defined in the 3GPPTS 36.211 document.

FIG. 3C is a functional block diagram illustrating a block sequence 302of example blocks executed to communicate a transmission scheme in awireless communication system. In block 304, a first precoding matrix isassigned to a first OFDM symbol. A second precoding matrix is assignedto a second OFDM symbol, in block 306, the second precoding matrix beingdifferent from the first precoding matrix.

FIG. 3D depicts an apparatus 308 for wireless communication (e.g., a UE120) comprising a module 310 for assigning a first precoding matrix to afirst OFDM symbol. A module 312 is provided to assign a second precodingmatrix to a second OFDM symbol, the second precoding matrix beingdifferent from the first precoding matrix.

It should be noted that, in alternative aspects of the presentdisclosure, the different precoder used in each OFDM symbol in FIG. 3Bmay be derived by permuting the columns of the precoding matrices. Ineither aspect, whether the different precoding matrix is selecteddirectly from the library of precoding matrices or the selectedprecoding matrix is permuted, the eNB 110 and the UE 120 should bothknow the sequence of precoding matrices utilized in each OFDM symbol.For example, the UE 120 may use a pseudo random sequence that the eNB110 also knows.

FIG. 4 and FIG. 5 show example precoder assignments in precoder matrixcycling sequences 400 and 500. For example, assume that R is thetransmission rank and M is the codebook size. In one design, e.g., asdepicted in FIG. 4, a k^(th) precoder (element 402) may simply be the (kmod M)^(th) precoding matrix for rank R in the 3GPP TS 36.211 document.Precoder element 402 is used in OFDM symbol 301-0 (FIG. 3B). In anotherdesign, e.g., as depicted in FIG. 5, (k·R)^(th) precoder (element 502)could be the (k mod M)^(th) precoding matrix in the 3GPP TS 36.211document. The other precoders, (k·R+1, k·R+2, . . . , k·R+R−1)^(th)precoders (elements 504, 506, 508, 510, and 512) may be column permutedversion of the (k mod M)^(th) precoding matrix.

Precoder element 504 is the precoder matrix of precoder element 502after a single permutation. The third column of precoder element 504 isthe first column of precoder element 502. The first permutation resultsfurther in the second column of precoder element 502 now being the firstcolumn of precoder element 504 and the second column of precoder element504 being the third column of the precoder element 502. The transmissionrank R of FIG. 4 and FIG. 5 is 3, thus each precoder matrix comprisesthree columns and may be permuted three times to achieve a differentprecoder matrix within a single transmission stream. Precoder elements502, 504, and 506 are used in OFDM symbols 301-0, 301-1, and 301-2 (FIG.3B). Precoder element 508 is a new precoding matrix selected from theknown library and is permuted three times for precoder elements 510 and512. The precoder elements 508, 510, and 512 are used in OFDM symbols301-4, 301-5, and 301-6 (FIG. 3B).

The alternative aspect of the disclosure that uses permutations of theselected precoder matrices provides a middle option, between thestandard of using the same precoder matrix for each OFDM symbol and theadditional alternative aspect of the disclosure that selects a newprecoding matrix directly from the known library of precoding matrices.By permuting the columns of a particular precoding matrix and applyingto different OFDM symbols, even though different spatial layers seedifferent channel conditions in on OFDM symbol, it is expected that thechannel conditions for each spatial layer averaged over those OFDMsymbols will be similar, which will render similar terminationstatistics for all code words.

In another design a new DCI syntactical message may be introduced for ULMIMO transmission. Currently, two transmission schemes are defined inuplink transmissions: (1) single antenna, single-input, multiple-output(SIMO); and (2) multiple antenna, multiple-input, multiple-output(MIMO). However, it would be beneficial in multi-antenna uplinktransmissions to have additional transmission schemes. For example,lower geometry UEs may benefit from rank-1 closed-loop beamforming,while higher geometry UEs with a high Doppler will benefit fromopen-loop beam-forming or spatial multiplexing. Thus, in addition to thecurrent standard transmission schemes, it would be beneficial to defineadditional open-loop transmission schemes, such as rank-1 open-loopbeamforming and higher-rank open-loop spatial multiplexing. However,under the current standards, DCI messages cannot handle more than theexisting two transmission schemes.

As explained further below, a new DCI message is defined that allowsscheduling of either rank-1 closed-loop beamforming or higher rankopen-loop spatial multiplexing using a single DCI message transmission.This new DCI message format includes a control entry that, depending onthe value of the control entry, the various fields of the DCI messagemay be interpreted according to a different set of rules.

Table 1 provides an example format of the new DCI message. In otherdesigns, the various fields may be arranged differently.

TABLE 1 DCI format for 2 Transmit Antennas Field Bit Width Notes MCS 5modulation and coding scheme NDI_1 1 first new data indicator RI 1 rankindicator NDI_2 1 second new data indicator PMI 5 precoding matrix indexothers X resource block assignment, power control, etc total payload X +13

With reference to Table 1, the MCS field represents an index to amodulation and coding scheme. NDL_1 and NDI_2 are two new data indicatorbits and are used as further described below. Since a configuration with2 transmit antennas may have rank 1 or 2, a single bit RI is used toconvey the rank information. PMI represents a precoding matrix index(e.g., an index to the sequence as depicted in FIG. 3 or FIG. 4), asfurther explained below. Other data fields of varying lengths,collectively represented as X, may be included, as is well known in theart. For the aspect of the DCI message referenced in Table 1, thecontrol entry is the rank indicator (RI). Depending on the value of RI,the different fields of the DCI message will be interpreted differently.

For example, when RI is set to 0 by the eNodeB 110, a single transportblock (TB) is to be transmitted because the communication channel hasrank 1. The UE 120, therefore, performs rank-1 beamforming for a singleTB transmission. NDU denotes whether the TB to be transmitted is a newtransmission or a re-transmission. With RI=0, NDI_2 denotes the index ofthe enabled TB (the TB being transmitted, in case of a re-transmission).NDI_2 bit may not be useful for a new transmission, but in the case of are-transmission, NDL_2 indicates which block is to be retransmitted.With the 5-bit PMI field, 32 different code points (indices) arepossible. In one design, 6 codepoints may be used for signaling aprecoding vector for rank-1 closed-loop beamforming. One of theremaining 26 codepoints may be utilized to signal that the transmissionis to be an open-loop rank-1 transmission. This signaling may be used,for example, when performing a rank-1 precoding vector switching overOFDM symbols. The unused code points may be reserved for future use.

When RI is set to 1, the UE 120 may perform open-loop MIMO with adifferent precoding matrix sequence (PMS) per OFDM symbol (e.g., asshown in FIGS. 3 and 4). When two TBs are to be transmitted withtransmission rank 2, NDI_1 may denote whether TB_1 is a new transmissionor a re-transmission. With RI=1, NDI_2 may denote whether TB_2 is a newtransmission or a re-transmission. The 5-bit MCS field may signal theMCS for the first TB and, in the RI=1 case, the 5-bit PMI field may beinterpreted by the UE 120 to represent the MCS for the second TB.

Table 2 provides an example DCI message format when a UE 120 has fourtransmit antennas. The various fields listed in Table 2 may be used inany predefined order.

TABLE 2 DCI format for 4 Transmit Antennas Field Bit Width Notes MCS 5modulation and coding scheme NDI_1 1 first new data indicator RI 2 rankindicator NDI_2 1 second new data indicator PMI 5 precoding matrix indexothers X resource block assignment, power control, etc total payload X +14

Here again, RI is the control entry of this aspect of the DCI message.When the eNodeB 110 sets RI to 0, it is an indication to the UE 120 toperform rank-1 beamforming (because a single TB is to be transmitted).When a single TB is to be transmitted, NDI_1 denotes whether this is anew transmission or a re-transmission and NDI_2 dictates index of theenabled TB, similar to previously described with respect to Table 1. Ofthe 32 codepoints possible with the 5-bit PMI field, 24 codepoints maybe used for signaling the precoding vector for rank-1 closed-loopbeamforming. One of the remaining codepoints may be utilized forsignaling of rank-1 open-loop transmission. Another one of the remainingseven codepoints may be utilized for signaling rank-2 open-loop MIMOoperation. For example, this value of codepoint may be used to handlethe scenario where a TB mapped onto 2 layers is re-transmitted.

When RI is set to 1, 2, or 3, this is an indication to the UE 120 to doopen-loop MIMO by applying a different precoding matrix per OFDM symbol.In a four-antenna configuration, the UE 120 may perform an initial rank3/4 transmission by mapping a single TB to two layers. NDL_1 may denotewhether TB_1 is a new transmission or a re-transmission, and NDI_2 maydenote whether TB_2 is a new transmission or a re-transmission. The5-bit MCS field may signal the MCS for the first TB, and, in the RI=1,2, or 3 cases, the 5-bit PMI field may be used to signal the MCS for thesecond TB.

FIG. 6 is a functional block diagram illustrating a block sequence 600of example blocks executed to communicate a transmission scheme in awireless communication system. In block 602, a selected transmissionscheme is identified from multiple transmission schemes suitable for UEuplink communication. A control element associated with the selectedtransmission scheme is selected in block 604. A DCI message isgenerated, in block 606, using the control element and a set ofparameters uniquely associated with the selected transmission scheme.The DCI message is then transmitted, in block 608, to the UE.

FIG. 7 depicts an apparatus 700 for wireless communication (e.g., a UE120) comprising a module 702 for identifying a selected transmissionscheme from multiple transmission schemes suitable for UE communication.Module 704 is provided to select a control element associated with theselected transmission scheme. Module 706 is for generating a DCI messageusing the control element and a set of parameters uniquely associatedwith the selected transmission scheme. The module 708 is provided totransmit the DCI message to the UE.

FIG. 8 is a functional block diagram illustrating a block sequence 800of example blocks executed to communicate a transmission scheme in awireless communication system. In block 802, a downlink control messageis received from a base station. A control element is read, in block804, from the downlink control message. In block 806, an uplinktransmission scheme is set based on the control element. A set ofinterpretation rules uniquely associated with the control element isdetermined in block 808. A set of parameters within the downlink controlmessage are then interpreted, in block 810, according to the set ofinterpretation rules.

FIG. 9 is a depiction of a wireless communication receiver apparatus900. Module 902 is provided for receiving a downlink control messagefrom a base station. Module 904 is for reading a control element fromthe downlink control message. Module 906 is provided to set an uplinktransmission scheme based on the control element. A module 908 is fordetermining a set of interpretation rules uniquely associated with thecontrol element. Module 910 is provided for interpreting a set ofparameters within the downlink control message according to the set ofinterpretation rules.

As will be appreciated, the new DCI messaging procedure described hereinenables signaling of either rank 1 closed loop beamforming, open-loopbeamforming, or a higher rank (e.g., 2, 3, or 4) open loop spatialmultiplexing using the same syntax (e.g., single DCI format). A controlelement in a field of the new DCI message indicates to a UE 120 thetransmission scheme and the particular set of rules to use ininterpreting the set of parameters associated with the selectedtransmission scheme found in the DCI message. New fields are also addedin order to accommodate the potential transport of multiple transportblocks.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, and algorithm steps described in connectionwith the disclosure herein may be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on a non-transitorycomputer-readable medium. Non-transitory computer-readable mediaincludes computer storage media and the like. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Disk and disc, asused herein, includes compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk and blu-ray disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method of wireless communication, comprising:identifying a selected transmission scheme from a plurality oftransmission schemes suitable for user equipment (UE) communication;selecting a control element associated with the selected transmissionscheme, wherein the control element indicates to a UE at least theselected transmission scheme and a set of rules for interpreting a setof parameters associated with the selected transmission scheme, whereinthe set of rules is dependent on the selected control element;generating a downlink control information (DCI) message using thecontrol element and the set of parameters; and transmitting the DCImessage to the UE.
 2. The method of claim 1, wherein the control elementis a rank indicator.
 3. The method of claim 1, wherein the selectedtransmission scheme is one of: a closed-loop beamforming transmission,an open-loop beamforming transmission, and an open-loop spatialmultiplexing transmission.
 4. An apparatus for wireless communication,comprising: means for identifying a selected transmission scheme from aplurality of transmission schemes suitable for user equipment (UE)communication; means for selecting a control element associated with theselected transmission scheme, wherein the control element indicates to aUE at least the selected transmission scheme and a set of rules forinterpreting a set of parameters associated with the selectedtransmission scheme, wherein the set of rules is dependent on theselected control element; means for generating a downlink controlinformation (DCI) message using the control element and the set ofparameters; and means for transmitting the DCI message to the UE.
 5. Theapparatus of claim 4, wherein the control element is a rank indicator.6. The apparatus of claim 4, wherein the selected transmission scheme isone of: a closed-loop beamforming transmission, an open-loop beamformingtransmission, and an open-loop spatial multiplexing transmission.
 7. Anon-transitory computer-readable medium having program code recordedthereon, comprising: program code for causing a computer to identify aselected transmission scheme from a plurality of transmission schemessuitable for user equipment (UE) communication; program code for causingthe computer to select a control element associated with the selectedtransmission scheme, wherein the control element indicates to a UE atleast the selected transmission scheme and a set of rules forinterpreting a set of parameters associated with the selectedtransmission scheme, wherein the set of rules is dependent on theselected control element; program code for causing the computer togenerate a downlink control information (DCI) message using the controlelement and the set of parameters; and program code for causing thecomputer to transmit the DCI message to the UE.
 8. The non-transitorycomputer-readable medium of claim 7, wherein the control element is arank indicator.
 9. The non-transitory computer-readable medium of claim7, wherein the selected transmission scheme is one of: a closed-loopbeamforming transmission, an open-loop beamforming transmission, and anopen-loop spatial multiplexing transmission.
 10. An apparatus configuredfor wireless communication, the apparatus comprising: at least oneprocessor; and a memory coupled to the at least one processor, whereinthe at least one processor is configured to: identify a selectedtransmission scheme from a plurality of transmission schemes suitablefor user equipment (UE) communication; select a control elementassociated with the selected transmission scheme, wherein the controlelement indicates to a UE at least the selected transmission scheme anda set of rules for interpreting a set of parameters associated with theselected transmission scheme, wherein the set of rules is dependent onthe selected control element; generate a downlink control information(DCI) message using the control element and the set of parameters; andtransmit the DCI message to the UE.
 11. The apparatus of claim 10,wherein the control element is a rank indicator.
 12. The apparatus ofclaim 10, wherein the selected transmission scheme is one of: aclosed-loop beamforming transmission, an open-loop beamformingtransmission, and an open-loop spatial multiplexing transmission.
 13. Amethod for uplink communication in a wireless network, comprising:receiving a downlink control message from a base station; reading acontrol element from the downlink control message, wherein the controlelement indicates at least a transmission scheme and a set ofinterpretation rules for interpreting a set of parameters associatedwith the selected transmission scheme; setting an uplink transmissionscheme based on the transmission scheme indicated by the controlelement; determining the set of interpretation rules indicated by thecontrol element, wherein the set of interpretation rules is dependent onthe control element; and interpreting the set of parameters within thedownlink control message according to the set of interpretation rules.14. The method of claim 13, wherein the control element is a rankindicator.
 15. The method of claim 13, wherein the uplink transmissionscheme includes one of: a closed-loop beamforming transmission, anopen-loop beamforming transmission, and an open-loop spatialmultiplexing transmission.
 16. A wireless communication apparatus,comprising: means for receiving a downlink control message from a basestation; means for reading a control element from the downlink controlmessage, wherein the control element indicates at least a transmissionscheme and a set of interpretation rules for interpreting a set ofparameters associated with the selected transmission scheme; means forsetting an uplink transmission scheme based on the transmission schemeindicated by the control element; means for determining the set ofinterpretation rules indicated by the control element, wherein the setof interpretation rules is dependent on the control element; and meansfor interpreting the set of parameters within the downlink controlmessage according to the set of interpretation rules.
 17. The wirelesscommunication apparatus of claim 16, wherein the control element is arank indicator.
 18. The wireless communication apparatus of claim 16,wherein the uplink transmission scheme includes one of: a closed-loopbeamforming transmission, an open-loop beamforming transmission, and anopen-loop spatial multiplexing transmission.
 19. A non-transitorycomputer-readable medium having program code recorded thereon, theprogram code including: program code for causing the computer to receivea downlink control message from a base station; program code for causingthe computer to read a control element from the downlink controlmessage, wherein the control element indicates at least a transmissionscheme and a set of interpretation rules for interpreting a set ofparameters associated with the selected transmission scheme; programcode for causing the computer to set an uplink transmission scheme basedon the transmission scheme indicated by the control element; programcode for causing the computer to determine the set of interpretationrules indicated by the control element, wherein the set ofinterpretation rules is dependent on the control element; and programcode for causing the computer to interpret the set of parameters withinthe downlink control message according to the set of interpretationrules.
 20. The non-transitory computer-readable medium of claim 19,wherein the control element is a rank indicator.
 21. The non-transitorycomputer-readable medium of claim 19, wherein the uplink transmissionscheme includes one of: a closed-loop beamforming transmission, anopen-loop beamforming transmission, and an open-loop spatialmultiplexing transmission.
 22. An apparatus configured for wirelesscommunication, the apparatus comprising: at least one processor; and amemory coupled to the at least one processor, wherein the at least oneprocessor is configured to: receive a downlink control message from abase station; read a control element from the downlink control message,wherein the control element indicates at least a transmission scheme anda set of interpretation rules for interpreting a set of parametersassociated with the selected transmission scheme; set an uplinktransmission scheme based on the transmission scheme indicated by thecontrol element; determine the set of interpretation rules indicated bythe control element, the set of interpretation rules dependent on thecontrol element; and interpret the set of parameters within the downlinkcontrol message according to the set of interpretation rules.
 23. Theapparatus of claim 22, wherein the control element is a rank indicator.24. The apparatus of claim 22, wherein the uplink transmission schemeincludes one of: a closed-loop beamforming transmission, an open-loopbeamforming transmission, and an open-loop spatial multiplexingtransmission.